Radial blower for a leaf and waste collection/removal apparatus with operating noise suppression means

ABSTRACT

The radial blower for a leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus has a Helmholz resonator ( 14 ) for damping or attenuating sound generated by the blower. The Helmholtz blower ( 14 ) is connected to the sound conducting flow duct ( 12 ) of the blower ( 10 ) with a connector pipe ( 13 ). The sound resonance eigenfrequencies are adjusted by changing the cross-sectional area (A) of the connector pipe ( 13 ), the length (l) of the connector pipe ( 13 ) and/or the volume (V) of the Helmholz resonator.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a radial blower for a leaf and waste vacuum apparatus, leaf and waste blower apparatus or a leaf and waste loading apparatus with an operating noise damping or attenuating device.

[0003] 2. Description of the Related Art

[0004] Equipment for waste and leaf work includes vacuum devices, blowers and also loaders. All these tools have a radial blower, which is comparatively loud when it operates.

[0005] Currently only insignificant sound damping features are provided in this type of equipment, since this equipment is currently used only during daytime and people must put up with noise generated during daytime. However street cleaning operations already occur very early in the morning to remove leaves from streets and travel ways, since traffic on streets and travel ways is light during early morning hours. Furthermore new laws regarding sound or noise emission limit the use of this type of equipment in closed residential areas.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a radial blower for a leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus, which operates without generating noteworthy noise.

[0007] This object is attained by a radial blower for a leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus with a sound damping or attenuating device for noise or sound generated by the blower during operation of the blower. The sound damping or attenuating device has a Helmholtz resonator, which is mounted on a sound conducting flow duct of the blower. The Helmholtz resonators are especially outstandingly suitable for filtering low frequencies of the blower. High frequencies can be eliminated by sound absorbing devices, which can be additionally provided in the radial blower according to the invention.

[0008] At least one pipe connector can be used to connect the Helmholtz resonator with the sound conducting flow duct. It is particular advantageous when the sound resonance eigenfrequencies of the Helmholtz resonator are adjustable, since the highest sound absorbing efficiencies develop in the vicinity of its sound resonance eigenfrequencies. The adjustability of the eigenfrequencies can occur in different ways. The at least one pipe connector can be exchangeable or replaceable. It is thus possible to provide pipe connectors of different lengths or different diameters between the resonator and the sound conducting flow duct. The sound resonance eigenfrequencies are thus adjusted by changing from a pipe connector with one length or diameter to a pipe connector of another length or diameter.

[0009] However it is also possible to adjust the sound resonance eigenfrequencies by changing the cross-sectional area and/or the length of the at least one pipe connector. Thus in preferred embodiments the pipe connector, for example, is provided as a telescoping connector pipe. An insert can be provided to change the interior cross-sectional area of the pipe connector in other preferred embodiments.

[0010] Furthermore naturally it is also possible to change the sound resonance eigenfrequencies of the Helmholz resonator by varying its volume. For example the volume can be varied when the resonator has a movable wall that can be set at various positions or continuously adjusted.

[0011] Helmholtz resonators are generally cylindrical bodies. The pipe connector thus opens into the cylindrical wall of the Helmholtz resonator. However it is also possible to connect a Helmholtz resonator in series with the sound conducting flow duct. Generally however the flow properties of the blower system would be expected to be impaired when the Helmholtz resonator is connected in series with the flow duct. This is avoided with the branched resonator arrangement.

BRIEF DESCRIPTION OF THE DRAWING

[0012] The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the following figures, in which

[0013]FIG. 1 is a schematic cross-sectional view through a first embodiment of a radial blower according to the invention, in which the length of the pipe connector is fixed;

[0014]FIG. 2 is a schematic cross-sectional view through a part of a second embodiment of a radial blower according to the invention, in which the length of the pipe connector is changeable for adjustment of the sound resonance eigenfrequencies of the Helmholz resonator;

[0015]FIG. 3 is a schematic cross-sectional view through a part of a third embodiment of a radial blower according to the invention, in which the transverse cross-sectional area of the pipe connector is changed by means of an insert for adjustment of the resonance eigenfrequencies of the Helmholz resonator; and

[0016]FIG. 4 is a top plan view of a part of a fourth embodiment of a radial blower according to the invention, showing a Helmholz resonator with a movable wall for adjusting of the resonance eigenfrequencies of the Helmholz resonator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]FIG. 1 is a schematic drawing of a radial blower 10 of an otherwise unshown leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus. The radial blower 10 has a central air suction device 11, for example comprising an impeller or fan, and a flow duct 12 connected with the suction device 11, which is sound conducting. A pipe connector 13 is connected to the flow duct 12 between the mouth 12.1 of the flow duct 12 and the central air suction device 11. The pipe connector 13 connects the flow duct 12 to a Helmholtz resonator 14. The Helmholtz resonator 14 is a cylindrical body with volume V. The pipe connector 13 has a transverse cross-sectional area A (the diameter D of the pipe is shown in FIG. 1) and a length l.

[0018] In preferred embodiments of the invention shown in FIGS. 2, 3 and 4 the sound resonance eigenfrequencies of the resonator 14 and thus its sound damping properties or muffler properties are influenced by changing one or more of the geometric parameters of the Helmholz resonator 14 and/or pipe connector 13. These geometric parameters include the volume V of the Helmholz resonator, the cross-sectional area A of the pipe connector 13 and the length l of the pipe connector 13. The Helmholz resonator 14 can be exactly tuned to the sonic oscillator frequencies or oscillation behavior of the blower 10 by adjusting these three parameters, namely V, A and l. The shunt connection of the resonator shown in all the illustrated embodiments does not effect the flow properties of the blower 10.

[0019] In other embodiments more than one pipe connector 13 with different cross-sections and lengths can be arranged between the resonator 14 and the flow duct 12. The pipe connectors can all be open at the same time or alternately closed and opened. Because of that an optimum adjustment of the sound damping properties of the resonator 14 to the noise properties of the blower 10 is possible.

[0020] In the embodiment shown in FIG. 2 the pipe connector 13 is a telescoping connector pipe with means for securing it at a fixed length after a length adjustment. The length l of the pipe connector 13 is adjustable because of the telescoping feature and thus the noise suppression means, namely the connector pipe 13 and the resonator 14, are tuned to the central air suction device 11 to optimize operating sound suppression.

[0021]FIG. 3 shows an embodiment in which a pipe-shaped insert 19 is provided which changes the transverse cross-sectional area of the connector pipe 13 in order to tune the noise suppression means to the blower 10 for optimum operating sound suppression.

[0022]FIG. 4 shows a final embodiment in which the cylindrical Helmholz resonator 14 has a movable end wall 17 for changing the volume V of the Helmholtz resonator 14 and thus the sound resonance eigenfrequencies.

[0023] The disclosure in German Patent Application 102 47 550.4 of Oct. 11, 2002 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119.

[0024] While the invention has been illustrated and described as embodied in a radial blower for a leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.

[0025] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

[0026] What is claimed is new and is set forth in the following appended claims. 

We claim:
 1. A radial blower for a leaf and waste vacuum apparatus, a leaf and waste blower apparatus or a leaf and waste loading apparatus, said radial blower comprising a sound conducting flow duct (12) and a sound damping or attenuating device; wherein said sound damping or attenuating device comprises a Helmholtz resonator (14).
 2. The radial blower as defined in claim 1, wherein said Helmholtz resonator (14) is mounted on the sound conducting flow duct (12) by at least one pipe connector (13), said at least one pipe connector connecting the Helmholz resonator (14) with the sound conducting flow duct (12).
 3. The radial blower as defined in claim 1, wherein said Helmholtz resonator (14) has sound resonance eigenfrequencies and means for adjusting said sound resonance eigenfrequencies.
 4. The radial blower as defined in claim 2, wherein said at least one pipe connector (13) is exchangeable or replaceable by at least one other pipe connector having geometric parameters or dimensions that are different from those of said at least one pipe connector (13).
 5. The radial blower as defined in claim 2, wherein said at least one pipe connector (13) has a transverse cross-sectional area (A) and a length (l) and means for adjusting at least one of said cross-sectional area (A) and said length (l).
 6. The radial blower as defined in claim 5, wherein said at least one pipe connector (13) is a telescoping connector pipe, whereby said length (l) is adjustable.
 7. The radial blower as defined in claim 5, further comprising an insert (19) for said at least one pipe connector (13) for adjusting said cross-sectional area (A).
 8. The radial blower as defined in claim 1, wherein said Helmholtz resonator (14) has a volume (V) and said volume (V) is adjustable.
 9. The radial blower as defined in claim 8, wherein said Helmholtz resonator (14) has a movable wall (17) for adjusting said volume (V). 